The present invention relates to a buck converter for use with a DC brushed motor to provide variable speed motor control. More specifically, the present application relates to a PWM buck converter that eliminates the need for a bulky input filter.
FIGS. 1A and 1B, respectively, illustrate a schematic representation of a buck converter 1 for use in controlling a brushed DC motor M. In FIG. 1A, the motor M is ON (ON state). That is, the motor M is connected to the DC line via the switch SW1. In FIG. 1B, the motor M is OFF (OFF state). That is, the switch SW1 is open such that the motor is not connected to the DC line. A conventional buck converter such as converter 1 utilizes an input filter 2 in order to meet EMI requirements for a power generator. The filter 2 is sized to limit the ripple of the DC line current to an acceptable value. Typically, the filter 2 includes an inductor L and two capacitors C1, C2, for example, as illustrated in FIGS. 1A and 1B. The capacitors C1 and C2 are typically rather expensive and typically are large reservoir capacitors. Thus, the filter 2 tends to be relatively bulky and expensive.
Accordingly, it would be beneficial to provide a buck converter for controlling a motor that avoids the problems mentioned above.